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sudden dieback: what could cause it?

Posted by ataraxia 7a (My Page) on
Mon, Sep 2, 13 at 16:08

I moved into a new house a month ago, with three seemingly healthy and well-established rhododendrons in the garden. Suddenly they seem to be dying back. The one in the photo, which is the worst, looked fine less than a week ago.

I would really appreciate any advice you might have, because I don't know what to make of it.

The dieback is on multiple branches, and I don't see any evidence of pests. There is a shallow layer of bark mulch, but it's not right up against the plants. There is also a flowering dogwood in this garden, and it has what I would guess is powdery mildew, but now I wonder if the two issues could be related.

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RE: sudden dieback: what could cause it?

The two most common causes of sudden dieback are both fungal infections. Various strains of phytophthora cause root rot. This disease is more common in pots, but overwatering, high soil temperatures and poor drainage can lead to it in the landscape as well.

Botryosphaeria effects branches and stems and can appear suddenly - often as a result of droughty conditions. This is probably more common than phytophthora in the landscape.

Unfortunately, there are really no good treatment options once an infection has appeared. Pruning back to healthy green wood, cleaning up and disposing of any fallen leaves, and making sure growing conditions are the best you can provide are the best things you can do.

There's more good information available at rhodyman's website.

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